While a very large number of systems have been developed to save water in the flushing of water closets, most require unacceptable alterations to the mechanisms extant and therefore have not come into popular use.
Since the invention of the modern flushing water closet, about 1870, there have been many patents issued disclosing several fundamental concepts for saving water. The largest number of patents present two preset dump valve levels within a reservoir, each with its own valve and valve seat. The valves may be, generally, separately operated by a variety of novel means whereby the reservoir is emptied to either of two levels at the option of the operator. While the principle is sound, the modifications required to the existing water closets precludes their practical implementation. The second largest group of patents addresses multiple or divided reservoirs which, for economical reasons, are not likely contenders to deal with the predicted water supply and disposal crises. A variety of other means are presented including weighted floats and decreasing buoyancy float valves.
The main obstacle to the adoption of any of the schemes disclosed in the prior art is that of economics. Despite the preponderance of evidence that fresh water is becoming a scarce commodity and that sewage disposal presents an ever increasing problem, individuals are unwilling to undertake the cost and inconvenience of even modest conversions of their water systems. In the United States it has been determined that about forty-five percent of the domestically used water is consumed in the WC flushing process. Whereas such simple expediencies as placing a brick in the reservoir will conserve a small amount of water with each flush -- about five percent -- it does not solve the problem at hand.